1. Field of the Invention
The present invention relates to article transport devices.
2. Description of Related Art
Article transport devices have an endless revolving body that is configured to move along a cyclic path in a substantially horizontal direction and a plurality of article supports each of which supports an article. The plurality of article supports move together with the endless revolving body with the supports spaced apart from each other in a traveling direction.
Such article transport devices are used for transporting articles such as transport containers that contain semiconductor substrates to and from various article handling facilities such as article storage facilities that store the articles.
A revolving path in the endless revolving body is provided with an article delivering location for delivering articles to an article handling facility and an article receiving location for receiving articles from an article handling facility.
For example, in such conventional article transport devices, article placing members are installed in a fixed manner on an endless revolving body, article transferring means is provided at an article delivering location and an article receiving location on the outer side of the endless revolving body, and when the article transferring means operates a placing portion on which an article is placed and supported, the article is transported between the article placing member and an article handling facility (see International Publication No. WO 03/000472, for example).
In these conventional article transport devices, when the article transferring means takes an article out of the article placing member at the article delivering location, first, the placing portion is moved in synchronization with the movement of the article placing member in a revolving direction of the endless revolving body. Next, in a state where the placing portion is moved in synchronization with the movement of the article placing member, the placing portion is projected below the article that is supported by the article placing member, and is then raised, so that the article is supported by the placing portion, and then the placing portion is withdrawn.
Furthermore, when the article transferring means loads an article onto the article placing member at the article receiving location, in a state where the placing portion is moved in synchronization with the movement of the article placing member, the placing portion is projected such that the article that is supported by the placing portion is positioned above the article placing member, then the placing portion is lowered, so that the article is loaded onto the article placing member, and then the placing portion is withdrawn.
After the article transferring means takes an article out of the article placing member at the article delivering location, the placing portion is moved, for example, the placing portion that supports the article is moved toward the article handling facility in order to transport the taken out article to the article handling facility, then the placing portion is moved to a start position for receiving a next article.
Furthermore, after the article transferring means loads an article onto the article placing member at the article receiving location, the placing portion is moved, for example, the placing portion is moved toward the article handling facility in order to receive an article from the article handling facility, then the placing portion is moved to a start position for moving the placing portion in synchronization with the movement of the article placing member when loading the article onto the article placing member at the article receiving location.
In this manner, in a state where the placing portion is moved in synchronization with the movement of the article placing member, when the placing portion is projected, vertically moved, and withdrawn by the article transferring means, articles are transported between the article placing member and the article handling facility without stopping the endless revolving body revolving in a circular manner while articles are transferred to and from the article placing member.
In these conventional article transport devices, at the article delivering location and the article receiving location, when the article transferring means takes an article out of the article placing member for transfer or loads an article onto the article placing member for transfer, the placing portion of the article transferring means is put on standby at a movement start position. When the article placing member for transfer reaches a position corresponding to the movement start position, the placing portion is projected toward the article placing member while the placing portion is moved in synchronization with the movement of the article placing member for transfer. Next, the placing portion is vertically moved, and an article is taken out of the article placing member or loaded onto the article placing member, and then the placing portion is withdrawn. At that time, the placing portion moves over a long distance in which the article placing member moves during the total time of a time necessary to project the placing portion, a time necessary to vertically move the placing portion, and a time necessary to withdraw the placing portion. Since it is necessary to move the placing portion over a long distance, the article transferring means has a large and complex configuration.